Are needles illegal to carry in a car?

syringes, generally no, unless theyve been used. also if theyve been used for drugs then almost always yes, tho it depends on the jurisdiction.

for example, in South Carolina its illegal to have a syringes with traces of cocaine, yet heroin residue is legal.

used needles could be illegal even if legitimate if not stored properly. many jurisdictions have laws against infectious material/improper disposal.

tattoo needles are often illegal as well if not properly steralized or disposed of after use.

but clean, never before used tattoo needles or syringes, yes they are almost always legal, though do expect some interrogation from the police and possibly getting your car torn apart in their war on drugs.